General anaesthesia and total hip replacement

Decreases in arterial oxygen tension (PaO2) and increased venous admixture (Qs/Qt) occur with acrylic cement insertion. Mean decreases in PaO2 of 17.5 mm Hg occurred in this study of 41 patients. Qs/Qt increased by 7 per cent to 16.0 per cent during general anaesthesia with N2O.O2 - Halothane (4L:2L:1%) and d-tubocurarine. Assessment of pulmonary gas exchange using PaO2, A-aDO2, a-ADCO2 and acid-base studies using arterial and central venous blood samples in 16 patients suggest that both ventilation-perfusion mismatch and pulmonary arterio-venous shunts occur transiently after acrylic bone cement is used. Stable central venous oxygen tensions and normal heart sounds (Doppler), heart rhythm and stable blood pressure suggest that cardiac output changes, if any, are minimal.